Nondestructive testing of materials using ultrasonic waves in order to determine the presence of cracks, flaws, inclusions, etc., in, for instance, metallic structures, is well known to those skilled in the art. Such procedures are commonly utilized to test materials prior to their installation, or materials which have already been installed and in service for a period of time. For example, the ultrasonic testing of metallic objects used in fastening or structural components of aircraft may be accomplished prior to their installation. Likewise, nondestructive ultrasonic examination of such components may be performed after some substantial period of aging. In both cases, the nondestructive testing is intended to identify failure-inducing flaws prior to an actual failure.
Nondestructive testing with ultrasonic imaging is also utilized in the detection of diseased tissue, as in U.S. Pat. No. 4,817,015, Insana et al., wherein tissue signatures were obtained from first and second order statistics of an image texture in order to discriminate between normal and abnormal tissue conditions. The process characterized tissues by statistically comparing the back scatter properties of tissues estimated from wave form statistics resulting from the mean spacing of periodic tissue scatterers over the test tissue.
However, none of the prior art discloses a method for statistically determining the presence of aging-related conditions in a structure which are the precursors to failure-related flaws, such as cracks. In spite of the obvious usefulness of such a process, there has not been provided a method for accomplishing this result.